The present invention relates to a thick waterstop layer utilizing bentonite or bentone (modified bentonite) particles, embedded in layers of adhesive that will keep the particles in position after repeated exposure to liquids that cause swelling. The waterstop provides a conforming liquid stopping layer in seams or joints between poured concrete layers.
Reference is made to a water barrier sheet shown in U.S. Pat. No. 4,693,923, which is made up of a plurality of individual layers of bentonite adhered to each other and to an underlying impervious sheet. Patent '923 illustrates adhesive spray bars and material feed hoppers usable in a new arrangement for making the strip of the present invention, and thus reference to this patent provides details of adhesives that are usable, as well schematic illustrations of adhesive feed controls and on and off controls. However, the device shown in U.S. Pat. No. 4,693,923, does not produce a thick layer of particulate bentonite, in the range of one-half to one inch thick, economically.
It has also been found that the ratio of adhesives to particles should be more when the material is used as a waterstop strip, and in the present invention, which provides an extremely thick waterstop strip made up of individual layers of bentonite adhered together with adhesive, a higher concentration of adhesive is desired. Further maintenance of void spaces between the bentonite particles is desirable to provide for conformability when the waterstop strips are compressed.
Additionally, U.S. Pat. No. 4,837,085 illustrates a prior waterstop strip, and illustrates the type of application to which the improved waterstop strip of the present application will apply.
Further, the use of overlying mesh fabrics, and also support mesh fabrics for bentonite has been known.
In each of these situations, however, the thickness of the layers of bentonite particles, is substantially less. Use of selected bentonite size particles permits the building up of a strip of substantial thickness to provide for full hydration in concrete work at the interface between two pourings, and interstitial spaces which make the strip able to conform to irregular concrete surfaces such as might be formed by workmans foot print or a chip from the concrete footings.